Descaling copper rods

ABSTRACT

Copper rods which are coated with an oxide scale are descaled and brightened by introducing the rod at a temperature of from 800* to 1,600* F. into a descaling zone which is substantially free of oxygen. While in the descaling zone, the rod is exposed to an atmosphere which contains at least 50 percent by volume of vapors of an organic compound. The organic compound is a lower alkyl monohydroxy alcohol, a lower alkyl polyhydroxy alcohol, a lower alkyl ketone or a mixture of any of these materials. After the reaction in the descaling zone is completed, the rod is quenched in an aqueous coolant without exposure to an oxidizing environment.

United States Patent [56] References Cited UNITED STATES PATENTS2,643,961 6/1953 Snyder et al. l48/l 3.2

Primary Examiner-Richard 0. Dean Attorney- Pennie, Edmonds, Morton,Taylor and Adams ABSTRACT: Copper rods which are coated with an oxidescale are descaled and brightened by introducing the rod at atemperature of from 800 to l,600 F. into a descaling zone which issubstantially free of oxygen. While in the descaling zone, the rod isexposed to an atmosphere which contains at least 50 percent by volume ofvapors of an organic compound. The organic compound is a lower alkylmonohydroxy alcohol, a lower alkyl polyhydroxy alcohol, a lower alkylketone or a mixture of any of these materials. After the reaction in thedescaling zone is completed, the rod is quenched in an aqueous coolantwithout exposure to an oxidizing environment.

PATENTEDuuv 16 Ian 3, 620,853

INVENTORS CLERMONT J.SNYDER JACK P. MOORE BY B r). MM f.

ATTORNEYS DESCALING COPPER nous This invention relates to a process forthe descaling and brightening of a copper rod to eliminate an oxidescale therefrom, and in particular, to a process for the descaling of acopper rod in which the rod is exposed to vapors of an organic compoundat elevated temperatures.

Copper rods from which copper wire is drawn are commonly formed by thehot-rolling of cast copper wire bars. The hot-rolled copper rod isusually circular in cross section and commonly about five-sixteenthsinch or three-eighths inch in diameter. Since the hot-rolling operationis normally carried out in the open air, the resulting copper rod isusually completely covered with an oxide scale, some of which is onlyloosely adherent to the underlying metal. In order to produce the finalcopper product, the hot-rolled copper rods are colddrawn into wire. Thepresence of the oxide scale on the copper rod during cold-drawing wouldgenerally result in defective wire and would cause severe wear problemswith respect to the dies used in the cold-drawing operation. Therefore,the oxide scale must be removed before the rod is colddrawn.

One procedure long used for removing scale from copper rod involvesimmersing the rod in a dilute sulfuric acid solution. In this procedure,commonly known as pickling, black cupric oxide scale is readily removed,but the underlining and more firmly adherent cuprous oxide scale may beonly partially removed. Another known procedure used to insure thoroughremoval of the oxide scale involves drawing the rod (usually afterpickling) through a shaving die by which a thin shaving of the rodsurface is mechanically removed.

Other procedures for removing scale from copper rods have also beendeveloped. One such process that has enjoyed mark success involvesexposing the rod to an atmosphere containing a halide vapor or a halogenat a temperature below 700 F., then heating to a dull red heat (e.g.,about l,200 F and then cooling to room temperature. This procedureresults in the formation of a scale which separates readily and leavesthe surface of the rods clean, free of dust and slivers, and free ofobjectionable pits.

These commercially used descaling procedures have a common disadvantage.All of these processes involve the consumption of a substantial part ofthe copper rods in the form of a scale loss or scrap. Generally, thisloss amounts from about 1 percent to as much as 5 percent of the weightof the rods. in view of this large copper loss, special reclaimingprocedures are necessary to recover the metal values of the scale scrapor pickle liquor to make the cleaning process economically feasible. Thereclaiming procedure of course increases the cost of the final copperproduct.

It is known that copper oxide may be readily reduced to metallic copperby heating the oxide in a reducing atmosphere. One successful processfor removing the oxide scale from copper rods by heating in a reducingatmosphere is found in our copending application Ser. No. 749,013, filedJuly Ill, 1968 now US. Pat. No. 3,546,029. Another successful processinvolves inductively heating the copper rod to a temperature above l,100F. (up to l,400 F.) and exposing the copper rod to a reducing atmosphereto reduce the oxide scale to metallic copper and is found in ourcopending application Ser. No. 812,283, filed Apr. 1, 1969.

We have devised an improved process of character described which isperformed in an atmosphere containing vapors of an organic compoundwhich atmosphere is substantially free of uncombined oxygen but whichmay contain substantial amounts of water vapor, and thereby we haveovercome the shortcomings and inadequacies of the prior art methodswhile obtaining excellent descaling and brightening of copper rods.

The present invention contemplates a simple, relatively inexpensive,nontoxic and eificient process for descaling and brightening a copperrod having oxide scale on its surface which comprises introducing therod at a temperature from about 800 F. to about l,600 F. into adescaling zone which is substantially free of oxygen. The rod is exposedin the zone directly to an atmosphere containing at least 50 percent byvolume of vapors of an organic compound. The organic compound is a loweralkyl monohydroxy alcohol, a lower alkyl polyhydroxy alcohol, a loweralkyl ketone or a mixture of any of these materials. The reactionbetween the oxide scale and the organic vapors is over in a short amountof time. Afier about a 3-second exposure in the descaling zone, thecopper rod is substantially free of the oxide scale. After exposure tothe organic compound vapor the rod is quenched without exposure to anoxidizing environment in an aqueous coolant bath to a temperature belowthat at which any substantial reoxidation of the copper can occur. Thebath is in communicating relation with the descaling zone, and as aresult the presence of water vapor in the descaling zone is permitted.

In performing the method of the invention, a copper rod with oxide scaleon its surface is introduced into a descaling zone comprising, forexample, an elongated or tubular chamber. The rod may be passedcontinuously through the descaling zone in which the organic vaporatmosphere is maintained. The rod may be heated to the requiredtemperature immediately prior to or even after entering the descalingzone, or it may come directly from a hot-rolling operation. Heating maybe by any desired means. For example, it may be accomplished in anexternally heated furnace or oven, or it may be by induction heatingeither within or without the descaling zone, or it may be by retentionof the heat of a prior hotrolling operation. Heating may be accomplishedas the rod passes continuously along, or alternatively, a coil ofoxidized rod may be heated to the required temperature, and then treatedbatchwise in the descaling chamber. In any event, the copper rod shouldbe at a temperature of from about 800 F. to about 1,600" F. when it issubjected to reaction in the descaling chamber. The range from 1,100 F.to l,300 F. is eminently suitable for the reaction.

Following the introduction of the rod into the descaling chamber theheated copper rod is directly exposed to an atmosphere comprising vaporsof the organic compound. For this purpose, a lower alkyl monohydroxyalcohol, a polyhydroxy alcohol, a lower alkyl ketone, or a mixturethereof is placed in a suitable vessel within the descaling chamber andheated by some heating source to form within the chamber an atmospherecomprising a substantial proportion of vapors of the organic compound.Examples of some of the organic compounds which are included within theinvention are such organic compounds as methyl alcohol, ethyl alcohol,butyl alcohol, isopropyl alcohol, ethylene glycol, methyl ethyl ketone,acetone and cyclohexanone. It is important to note that the atmospherewithin the descaling zone should be substantially free of oxygen so asto avoid the formation of any additional oxide scale on the surface ofthe copper rod, or combustion of the organic vapor. However, theatmosphere may without disadvantage contain a substantial amount ofwater vapor. The presence of the water vapor in the atmosphere generallyresults from the descaling chamber being in communicating relation withthe quenching bath; and does not interfere with the reducing operationnor does it effeet the finish on the copper rod. However, the presenceof the water vapor in the atmosphere may also result from using amixture of the organic compound and water. A mixture of a lower alkylalcohol with water (25 to 75 percent by volume of alcohol) may be used,for example, an ethyl alcohol-water mixture in the ratio of l to l or 1to 2.

After the oxide scale has been reduced to metallic copper, the rod isimmediately quenched in an aqueous liquid coolant to a temperature belowthat at which any substantial reoxidation of the copper can occur, e.g.,below about F. This is best achieved by positioning the exit end of thedescaling chamber below the surface of the aqueous liquid coolantwhereby the rod will pass directly from the reducing atmosphere withinthe chamber into the coolant without intervening exposure to theatmosphere. The coolant is held in a suitable container or trough (whichmay be open to the atmosphere) and may be circulated through a heatexchanger to extract the heat transferred to it from the copper rod. Anyloose reduced copper powder which remains on the rod surface afterquenching can be removed by a water spray. The copper rod emerging fromthe descaling chamber into the aqueous liquid coolant is free of oxidescale and is well suited for cold-drawing in normal wire-drawingoperations.

Another embodiment of the invention involves utilizing the organic vaporto clean, or prevent scale formation on, hot rods being rolled in aclosed system. in a process where copper rod is produced continuously,e.g., a continuous casting process, the rod while still hot(approximately l,500l,700 F.) may be rolled to final size in acontinuous operation. in such an operation the rod while still at atemperature of approximately 800-l ,200" F. and perhaps having someoxide scale on its surface, may be fed to a series of rolling millswhich are sealed from the air so as to enable maintaining an atmosphereabout them substantially free of oxygen. in rolling the copper rod insuch mill, the rod while still hot is lubricated and cooled with aconventional rolling emulsion to which has been added an organiccompound of a lower alkyl monohydroxy alcohol, a lower alkyl polyhydroxyalcohol, a lower alkyl ketone or a mixture of any of these organiccompounds. Examples of some of the specific organic compounds which canbe used are the same as stated above. The emulsion used can be any ofthe standard oil-water emulsions which are used as lubricant coolants inrolling operations; or in place of such emulsion a conventionallubricating oil may serve both as lubricant and coolant. The mixturefirst of emulsion (or lubricating oil) and organic compound acts as acoolant and as a lubricant, and most important to the present invention,upon contacting the hot copper rod, the organic compound in the mixtureforms a vapor which effects substantially complete reduction to metalliccopper of any oxide scale on the copper rod. If necessary, in order toavoid the formation of any additional oxide scale on the brightened rodsurface, the rod may be quenched in an aqueous coolant bath to atemperature below that at which any substantial reoxidation of thecopper can occur (e.g., below about 150 F.) prior to exposure to theair. Thus, the final copper product emerging from the rolling mill wouldbe substantially free from any oxide scale and need no pickling.

it is a significant advantage of the method of this invention that butlittle copper is lost as a result of the descaling operation. Typically,copper rod which is descaled as herein described will suffer a scaleloss in the range from 0.03 percent to 0.05 percent by weight of therod, as compared with losses from 20 to 50 times as great when descalingis accomplished by methods heretofore known.

An illustrative embodiment of one type of apparatus which is useful forperforming the present invention is now more particularly described withreference to the accompanying drawings wherein the sole FIGURE is aperspective view of a descaling chamber and an adjoining quench tank.

The apparatus shown in the FIGURE comprises a descaling chamber having arod entrance 11 and an exit end 12. The chamber is sealed tight in bothends by plates 13 and 14 so as to prevent any leakage of air into thechamber. Passing through the chamber is a tube 15. This tube hasnumerous perforations 16 located on that portion of its length inside ofthe descaling chamber.

A hot copper rod 17 is descaled by being continuously passed through thechamber 10. The descaling process can be performed as a continuousprocess(as illustrated in the drawing) or as a batch-type operationwherein, for example, the copper rod is in the form of a heated coil ofoxidized copper which is placed in the chamber. The copper rod can be atthe proper temperature prior to entering the chamber (by coming directlyfrom a hot-rolling operation) or can be heated to the proper descalingtemperature while it is in the chamber by, for example, introductionheating (not shown). in the illustrated operation, the rod may be causedto advance by the action of pinch rolls 18 or by the pull of a capstan(not shown) or by any other suitable means.

A coolant vessel 19 is positioned adjacent the rod exit end 12 of thedescaling chamber and is adapted to contain an aqueous liquid coolant,e.g., water, up to a normal level 20. The rod exit end of the descalingchamber is so positioned that it extends into the coolant vessel to aposition below the normal liquid level of the coolant. Thus, the copperrod 17 emerging from the descaling chamber passes directly into theaqueous coolant without coming into contact with the air. The coolantvessel may with advantage be in the form of a relatively long shallowtrough 21, equipped with guide rollers 22 for directing the rod 17 intoa substantially horizontal path for advancement through the coolantvessel.

inside the tube 15, at the rod entrance end 1 l, is a seal (not shown),which pennits the passage of the rod into the chamber but preventssubstantial leakage of air into the chamber or of organic vapors out ofthe chamber. At the rod exit end 12 the seal is provided by the coolant.Thus, aside from the passage of water vapor into the chamber from thecoolant vessel there can be no substantial gas or vapor leakage into orout of the descaling chamber.

Located at the bottom of chamber 10 is a vessel 23 which is used tocontain the liquid organic compound 24 within the chamber. immediatelybelow the vessel and outside of the chamber is a burner 25 which is usedto heat the organic compound to the proper temperature so that vapors ofthe compound can be formed. These vapors fill the chamber and passthrough the perforations 16 located in tube 15. Subsequently, the vaporscontact the oxide rod 17 and reduce the oxide scale on the surfacethereof.

We claim:

1. A method for descaling and brightening a copper rod having oxidescale on its surface which comprises:

a. introducing the rod at a temperature from about 800 to l,600 F. intoa descaling zone, said descaling zone being substantially free ofoxygen;

b. exposing the rod in the zone at said temperature directly to anatmosphere containing at least 50 percent by volume of vapors of anorganic compound selected from the group consisting of lower alkylmonohydroxy and polyhydroxy alcohols, lower alkyl ketones, and mixturesthereof, to effect substantially complete reduction to metallic copperof the oxide scale thereon;

c. thereafter quenching said rod without exposure to an oxidizingenvironment in an aqueous coolant bath to a temperature below that atwhich any substantial reoxidation of the copper can occur, said bathbeing in communicating relation with the descaling zone allowing thepresence of water vapor in the descaling zone.

2. The method according to claim 1 wherein the rod is at a temperaturefrom about 1, 1 00 to 1,300" F.

3. The method according to claim 1 wherein the descaling zone is anelongated region immediately surrounding the rod and the organiccompound is located in a container immediately below the rod.

4. The method according to claim 1 wherein the copper rod is ahot-rolled prior to descaling and is introduced into the descaling zonedirectly from the rolling operation while still hot.

5. The method according to claim 1 wherein the rod is inductively heatedto the descaling temperature.

6. The method according to claim 1 wherein the point at which the rodexits from the descaling zone is submerged below the surface of theliquid coolant.

7. The method according to claim 1 wherein the rod is continuouslypassed into and through the descaling zone.

8. The method according to claim 1 wherein the copper rod is in the formof a heated coil of oxidized copper and is treated batchwise in thedescaling zone.

9. The method according to claim 1 wherein the organic compound is amixture of a lower alkyl alcohol with water. said mixture containingabout 25 percent to 75 percent by volume of alcohol.

10. The method according to claim 1 wherein the organic compound is analcohol selected from the group consisting of methyl alcohol, ethylalcohol, butyl alcohol, isopropyl alcohol, and ethylene glycol.

11. The method according to claim 1 wherein the organic compound is aketone selected from the group consisting of methyl ethyl ketone,acetone and cyclohexanone.

12. A method for descaling and brightening a copper rod produced by acontinuous fonning operation and having an oxide scale on its surfacewhich comprises:

a. introducing the rod from the continuous forming operation at atemperature of about 800 to l,200 F. into a sealed rolling mill system,the atmosphere in said rolling mill system being substantially free ofoxygen,

b. having the rod in the rolling mill system at said temperature incontact with a mixture of a coolant lubricant and an organic compoundselected from the group consisting of lower alkyl monohydroxy andpolyhydroxy alcohols, lower alkyl ketones and mixtures thereof, toefiect substantially complete reduction to metallic copper of oxidescale thereon, and

c. cooling the rod without exposure to an oxidizing environment to atemperature below that at which any substantial reoxidation of thecopper can occur.

13. The method according to claim 12 wherein the coolant lubricant is anoil-water emulsion.

14. The method according to claim 12 wherein the organic compound isselected from the group consisting of methyl alcohol, ethyl alcohol,butyl alcohol, isopropyl alcohol, ethylene glycol, methyl ethyl ketone,acetone and cyclohexanone.

i t i i I

2. The method according to claim 1 wherein the rod is at a temperature from about 1,100* to 1,300* F.
 3. The method according to claim 1 wherein the descaling zone is an elongated region immediately surrounding the rod and the organic compound is located in a container immediately below the rod.
 4. The method according to claim 1 wherein the copper rod is a hot-rolled prior to descaling and is introduced into the descaling zone directly from the rolling operation while still hot.
 5. The method according to claim 1 wherein the rod is inductively heated to the descaling temperature.
 6. The method according to claim 1 wherein the point at which the rod exits from the descaling zone is submerged below the surface of the liquid coolant.
 7. The method according to claim 1 wherein the rod is continuously passed into and through the descaling zone.
 8. The method according to claim 1 wherein the copper rod is in the form of a heated coil of oxidized copper and is treated batchwise in the descaling zone.
 9. The method according to claim 1 wherein the organic compound is a mixture of a lower alkyl alcohol with water, said mixture containing about 25 percent to 75 percent by volume of alcohol.
 10. The method according to claim 1 wherein the organic compound is an alcohol selected from the group consisting of methyl alcohol, ethyl alcohol, butyl alcohol, isopropyl alcohol, and ethylene glycol.
 11. The method according to claim 1 wherein the organic compound is a ketone selected from the group consisting of methyl ethyl ketone, acetone and cyclohexanone.
 12. A method for descaling and brightening a copper rod produced by a continuous forming operation and having an oxide scale on its surface which comprises: a. introducing the rod from the continuous forming operation at a temperature of about 800* to 1,200* F. into a sealed rolling mill system, the atmosphere in said rolling mill system being substantially free of oxygen, b. having the rod in the rolling mill system at said temperature in contact with a mixture of a coolant lubricant and an organic compound selected from the group consisting of lower alkyl monohydroxy and polyhydroxy alcohols, lower alkyl ketones and mixtures thereof, to effect substantially complete reduction to metallic copper of oxide scale thereon, and c. cooling the rod without exposure to an oxidizing environment to a temperature below that at which any substantial reoxidation of the copper can occur.
 13. The method according to claim 12 wherein the coolant lubricant is an oil-water emulsion.
 14. The method according to claim 12 wherein the organic compound is selected from the group consisting of methyl alcohol, ethyl alcohol, butyl alcohol, isopropyl alcohol, ethylene glycol, methyl ethyl ketone, acetone and cyclohexanone. 